MODULATION OF ENDOTHELIN-1 PRODUCTION BY A PULMONARY EPITHELIAL-CELL LINE .1. REGULATION BY GLUCOCORTICOIDS

Endothelin-1 (ET-1) is one of the most potent bronchoconstrictor agent s yet described. Bronchial epithelial cells of asthmatic patients in v ivo express preproET-1 and in vitro release high amounts of ET-1. Heal thy and chronic bronchitic controls do not express preproET-1 or relea se ET-1. Interleukin-2 (IL-2) and other cytokines up-regulate the in v itro ET-1 release in guinea pig airway epithelial cells. We explored w hether two glucocorticoids, dexamethasone (Dex) and triamcinolone acet onide (TA), inhibit the synthesis and release of ET-1 by A549 cells, a transformed human pulmonary epithelial cell line, since ET-1 may have a basic role in the pathogenesis of asthma. Cells were grown to confl uence in RPMI 1640 plus 10% fetal bovine serum (FBS). Cells were then cultured for 3 days without serum to obtain ET-I basal levels. The eff ects of 10% FBS, IL-2 (10 U/mL), Dex, TA or mifepristone, a steroid an tagonist (1, 10 or 100 nM), were evaluated on ET-1 as measured by radi oimmunoassay (RIA). ET-1 production increased from 57.6 +/- 5 pg/mg ce ll protein at 6 hr to 170 +/- 9 pg/mg cell protein at 72 hr in control cultures. Ten percent FBS increased ET-1 production from 58.7 +/- 9.6 to 399 +/- 14.5 pg/mg cell protein. IL-2 significantly increased ET-1 from 100.7 +/- 6.1 to 144 +/- 6.7 at 24 hr and from 170 +/- 9 to 207. 7 +/- 24 at 72 hr. Dex and TA (10 and 100 nM) at 24-72 hr decreased ET -1 under basal conditions. Both drugs (only at 100 nM) decreased ET-1 production in 10% FBS- and IL-2-stimulated cells. Mifepristone (10 and 100 nM) reversed the decreased production of ET-1 induced by Dex (100 nM) at 24-72 hr. Northern blot analysis showed that Dex (100 nM) decr eased the expression of ET-1 mRNA at 6 and 24 hr, but that mifepriston e (100 nM) reversed this effect in cells cultured with Dex. In conclus ion, Dex and TA down-regulate the synthesis and production of ET-1 by this human pulmonary epithelial cell line under basal or stimulated co nditions, and these effects are reversed by mifepristone. These findin gs suggest a novel mechanism of glucocorticoid effect during the treat ment of asthma.